Many different patient support systems and sleep platforms have been designed that utilize individual or group bladder control to support a sleeper. The health benefits and sleep benefits of reducing pressure points on a sleeper are well documented. Such sleep platforms attempt to measure the force on a bladder, or a group of bladders, and reduce the pressure in the corresponding bladder(s) to effect pressure reductions in areas where high sleeper interface forces are detected.
Skinner et al., U.S. Pat. No. 7,883,478 describe a patient support having real time pressure control. Each bladder in this support is subtended by a force sensor that is able to sense a force that is transmitted through the inflatable bladder. The apparatus uses the force sensors to determine position and movement of a person lying on the bladders so that the bladder air pressure can be adjusted to match the person's position and movement. The apparatus controls individual bladder sections with individual pneumatic valves
Bobey et al., U.S. Pat. No. 7,698,765 describe a patient support having a plurality of vertical, inflatable bladders. The support system has an interior region that is defined by a top portion and bottom portion of a cover that define an interior region. Within the interior region can shaped bladders and force sensors are provided. The force sensors configured to measure pressure applied to one or more of the bladders. A separate sensor sheet is required to be external to the base and internal to the interior region that subtends the bladder region. Pressure transducers may be coupled to an individual bladder to measure the internal pressure of fluid within the bladder.
Gusakov, U.S. Pat. No. 5,237,501 describes an active mechanical patient support system that includes a plurality of actuator members that are controlled via a central processor. Associated with each actuator is a separate displacement transducer for determining the extension of the actuator. In addition, each actuator has a separate force sensor for determining the force on that actuator. A control means is provided to control the displacement of each actuator connected or integral to each actuator. In addition to individual force sensors associated with each individual actuator, a separate displacement transducer is utilized to determine the exact extension of each actuator member. This displacement transducer is required since the actuator is of a style that approximates a cylinder actuator. When loaded with a constant mass a cylinder actuator will maintain a constant subtended force measurement regardless of variations in the cylinder extension. Therefore, in order to determine the cylinder height, a displacement transducer is required.
Kramer et al., U.S. Pat. No. 7,409,735 describe a cellular person support surface. The support surface is composed of a plurality of inflatable cells, each of which has an associated pressure sensor corresponding to one of the plurality of inflatable cells. At the same time, each inflatable cell has one associated driver corresponding to one of the plurality of inflatable cells that is capable of inflating and deflating the associated cell. The patent requires an individual pressure sensor, as well as an individual inflation and deflation driver for each cell, or group of cells, that is being controlled. In the case of this patent, the sensors and drivers are located within the internal walls of the associated cell.
All of the existing patient support systems and sleep platforms suffer from the high cost and complexity associated with requiring individual control means, displacement transducers, and force sensors for each actuator. To mitigate this cost and complexity, some of these existing patient support systems and sleep platforms propose distributing both the control means and sensing means over multiple bladders or actuators. This requires that the multiple bladders or actuators be fluid coupled to one another and have one fluid stream interconnected between the multiple bladders. This results in a decreased ability to control and sense small areas of the sleep surface. The effect is an increased granularity in both sense and control of the sleep surface. Furthermore, the control means for controlling each actuator's displacement is both expensive and complex. The primary function of the subtended force sensors is to determine sleeper location and position, as well as absolute sleeper weight.
In all of the existing patient support systems and sleep platforms, a pressure sensor that subtends an actuator or bladder, or group of actuators or bladders, continues to read a constant force as long as the sleeper maintains his or her position. Some existing patient support systems and sleep platforms attempt to reduce the actuator pressure when a determination has been made, via the subtended force sensors, that the associated actuator or bladder is being subjected to forces above some established threshold force. By reducing fluid volume in the corresponding bladder, the height of that same bladder is also reduced. Once the fluid volume is reduced so that the corresponding height of the bladder is reduced to a level equal or below the surrounding bladders, the load on the bladder is partially or fully transferred to the surrounding bladders. This results in a pressure reduction on the sleeper from the above threshold bladder.
Beds and Mattresses have remained virtually unchanged over the centuries. Featherbeds are, from a technological point of view, little different from foam or spring beds. Once the aesthetically pleasing quilted mattress cover or ticking is removed, the actual active mattress components are little more than passive spring systems functioning in a similar manner to that of the feathers in a featherbed. All mattresses, whether they are made of individual coil springs, pocket coil springs, high tech foam, overall spring assemblies, or air bladders with adjustable firmness settings, passively adjust to a sleepers' movement. Even accounting for the latest adjustable firmness air bladder mattresses, the resulting active mattress component is nothing more than an adjustable firmness passive air spring. It is generally accepted that reducing high pressure points increases comfort and hence results in better sleep. Beyond reducing pressure points, no other active system has been proposed to improve sleep patterns. A sleep system that can optimize the underlying pressure profile of the sleeper in order to adaptively improve the resultant sleep patterns over several hours or days of sleep is needed.